alpha-Helical element at the hormone-binding surface of the insulin receptor functions as a signaling element to activate its tyrosine kinase
- Author(s)
- Whittaker, J; Whittaker, LJ; Roberts, CT; Phillips, NB; Ismail-Beigi, F; Lawrencee, MC; Weiss, MA;
- Details
- Publication Year 2012-07-10,Volume 109,Issue #28,Page 11166-11171
- Journal Title
- PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
- Publication Type
- Journal Article
- Abstract
- The primary hormone-binding surface of the insulin receptor spans one face of the N-terminal beta-helix of the alpha-subunit (the L1 domain) and an alpha-helix in its C-terminal segment (alpha CT). Crystallographic analysis of the free ectodomain has defined a contiguous dimer-related motif in which the alpha CT alpha-helix packs against L1 beta-strands 2 and 3. To relate structure to function, we exploited expanded genetic-code technology to insert photo-activatable probes at key sites in L1 and alpha CT. The pattern of alpha CT-mediated photo-cross-linking within the free and bound receptor is in accord with the crystal structure and prior mutagenesis. Surprisingly, L1 photo-probes in beta-strands 2 and 3, predicted to be shielded by alpha CT, efficiently cross-link to insulin. Furthermore, anomalous mutations were identified on neighboring surfaces of alpha CT and insulin that impair hormone-dependent activation of the intracellular receptor tyrosine kinase (contained within the transmembrane beta-subunit) disproportionately to their effects on insulin binding. Taken together, these results suggest that alpha CT, in addition to its hormone-recognition role, provides a signaling element in the mechanism of receptor activation.
- Publisher
- NATL ACAD SCIENCES
- Keywords
- 1ST 3 DOMAINS; MAMMALIAN-CELLS; LIGAND-BINDING; CROSS-LINKING; B-CHAIN; PROTEIN; CONFORMATION; SITE; RESOLUTION; EVOLUTION
- Research Division(s)
- Structural Biology
- Publisher's Version
- https://doi.org/10.1073/pnas.1205681109
- Open Access at Publisher's Site
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Creation Date: 2012-07-10 12:00:00